JP2013052387A - Multilayer microfiltration membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely provide one or more of desired throughput, sterility grade filtration, and robustness for membranes having isotropic (symmetric) and anisotropic (asymmetric) structures, e.g., multiple layer and composite membranes.SOLUTION: A microfiltration membrane comprises (a) an asymmetric layer, (b) an isometric layer, and (c) an interface layer between the asymmetric layer and the isometric layer, the interface layer having a first portion contacting the asymmetric layer and a second portion contacting the isometric layer: wherein, (i) the asymmetric layer has a region contacting the first portion of the interface layer, the region including cells having a first porous structure; (ii) the isometric layer has a region contacting the second portion of the interface layer, the region including cells having a second porous structure; the first porous structure being larger than the second porous structure; and the first portion of the interface layer comprises cells having the first porous structure, and the second portion of the interface layer comprises cells having the second porous structure. Methods of making and using the membrane are also disclosed.

Description

  [0001] Films having isotropic (symmetric) and anisotropic (asymmetric) structures, such as multilayers and composite films, are known in the art. However, conventional membranes have not been suitable for some applications. For example, the membranes did not reliably provide one or more of the following: one or more of the desired throughput, aseptic grade filtration, and robustness. .

  [0002] The present invention provides an improvement in at least some of the disadvantages of the prior art. These and other advantages of the invention will be apparent from the description set forth below.

  [0003] One embodiment of the present invention comprises (a) an asymmetric polymer layer, (b) an isotropic polymer layer, and (c) an interfacial polymer layer between the asymmetric layer and the isotropic layer. An interfacial polymer layer having a first portion in contact with the asymmetric layer and a second portion in contact with the isotropic layer; (i) the asymmetric layer is in contact with the first portion of the interface layer (Ii) the isotropic layer has a region in contact with the second portion of the interface layer, and the region has a second region. Including a cell having a pore structure, the first pore structure being larger than the second pore structure, wherein the first portion of the interface layer comprises a cell having the first pore structure, A microfiltration membrane is provided, wherein the two portions comprise cells having a second pore structure.

  [0004] In some embodiments, the asymmetric polymer layer and the isotropic polymer layer comprise different polymers, and the interfacial layer comprises a first polymer from the asymmetric layer and an isotropic layer. And a second different polymer.

  [0005] In some embodiments, the isotropic layer has a thickness of at least about 50 microns and / or the asymmetric layer has a thickness in the range of about 10 to about 15 microns.

  [0006] In some embodiments, the isotropic layer and the interfacial polymer layer are each in the range of about 15% to about 33% of the total thickness, and the asymmetric layer is about 60% of the total thickness. Within the range of ~ 70%.

  [0007] Another embodiment of the present invention provides: (a) a first asymmetric polymer layer having a first asymmetry rate; and (b) a second asymmetric rate greater than the first asymmetry rate. Two asymmetric polymer layers; (c) an interfacial polymer layer between the first asymmetric layer and the second asymmetric layer, a first portion in contact with the first asymmetric layer; and a second An interfacial polymer layer having a second portion in contact with the asymmetric layer, wherein: (i) the first asymmetric layer has a region in contact with the first portion of the interface layer, and the region has the first portion (Ii) the second asymmetric layer has a region in contact with the second portion of the interface layer, the region includes a cell having the second pore size, and the first pore size is the first The first portion of the interface layer comprises a cell having a first pore size, and the second portion of the interface layer comprises a cell having a second pore size. Providing a dense membrane.

  [0008] In some embodiments, the first asymmetric polymer layer and the second asymmetric polymer layer comprise different polymers, and the interface layer comprises a first polymer from the first asymmetric layer; And a second different polymer from the second asymmetric layer.

  [0009] In some embodiments, the first asymmetric polymer layer has an asymmetry ratio in the range of about 0.5 to about 1.5, and / or the second asymmetric polymer layer is about 2 It has the above asymmetry rate.

  [0010] In some embodiments including first and second asymmetric layers, the first asymmetric layer and the interfacial polymer layer together represent about 8% to about 15% of the total film thickness, The two asymmetric layers are about 75% to about 90% of the total film thickness.

  [0011] In some embodiments, the membrane is a wrinkled membrane.

  [0012] A precision according to an embodiment of the invention comprising an asymmetric layer, an isotropic layer, and an interface layer having a first portion in contact with the asymmetric layer and a second portion in contact with the isotropic layer The method of forming a filtration membrane includes: (a) preparing a first solution comprising a first polymer and a solvent for the first polymer; (b) a second polymer and the Preparing a second solution comprising a solvent for the second polymer; (c) casting the first solution onto the surface of the first support; and (d) a short time interval. Later, casting a second solution onto the first solution to form a pre-film, (e) exposing the pre-film to circulating air, and (f) the first solution in a non-solvent liquid And performing phase separation of the second solution. The first and second polymers may be the same or different.

  [0013] In another embodiment, a first asymmetric layer having a first asymmetry rate, a second asymmetric layer having a second asymmetry rate greater than the first asymmetry rate, and a first asymmetric layer And a method for forming a microfiltration membrane according to an embodiment of the present invention having an interface layer having a first portion in contact with the second asymmetric layer and a second portion in contact with the second asymmetric layer. Preparing a first solution comprising a molecule and a solvent for the first polymer; (b) a second comprising a second polymer and a solvent for the second polymer. Preparing a solution; (c) casting a first solution onto the surface of the first support; and (d) after a short time interval, casting a second solution onto the first solution. Forming a pre-film, and (e) a first solution and a second in a non-solvent liquid And a step of performing a phase separation of the solution. The first and second polymers may be the same or different.

  [0014] In another embodiment, a method of using a membrane, for example, for treating a fluid is provided.

Fig. 4 illustrates an exemplary general purpose system for producing a membrane according to an embodiment of the present invention showing a bed, first and second slot dies, a fan, and a quench bath. 1 shows a scanning electron microscope (SEM) cross-sectional view of one embodiment of a film according to the present invention, wherein the film has an isotropic layer, an asymmetric layer, and an interface layer. FIG. 4 shows a scanning electron microscope (SEM) cross-sectional view of another embodiment of a film according to the present invention, wherein the film has an isotropic layer, an asymmetric layer, and an interface layer. FIG. 6 shows another SEM cross-sectional view of one embodiment of a membrane according to another embodiment of the present invention, where the membrane has an isotropic layer, an asymmetric layer, and an interface layer. FIG. 4 shows a scanning electron microscope (SEM) cross-sectional view of another embodiment of a film according to the present invention, wherein the film has an isotropic layer, an asymmetric layer, and an interface layer. FIG. 4 shows another SEM cross-sectional view of another embodiment of a membrane according to the present invention, where the membrane has an isotropic layer, an asymmetric layer, and an interface layer. FIG. 4 shows another SEM cross-sectional view of another embodiment of a membrane according to the present invention, wherein the membrane has first and second asymmetric layers and an interface layer.

  [0022] The membrane according to the present invention includes (a) an asymmetric layer, a narrow asymmetry range accompanied by a gradual change in asymmetry, a pore structure of the asymmetric layer, and a pore structure of the isotropic layer. A first asymmetric layer having an asymmetric layer comprising a sharp demarcation between and a good adhesion between layers, or (b) a narrow asymmetry range with a gradual change in asymmetry; A second asymmetric layer having a wider range of asymmetry, a sharp demarcation between the pore structure of the first asymmetric layer and the pore structure of the second asymmetric layer, and good adhesion between the layers It is advantageous to have a second asymmetric layer comprising As a result, it is possible to obtain a highly durable membrane that exhibits high throughput and performs aseptic grade filtration as necessary.

  [0023] According to embodiments of the present invention, (a) an asymmetric polymer layer, (b) an isotropic polymer layer, and (c) an interfacial polymer layer between the asymmetric layer and the isotropic layer. An interfacial polymer layer having a first portion in contact with the asymmetric layer and a second portion in contact with the isotropic layer, and (i) the asymmetric layer includes a first portion of the interface layer; A region that contacts, the region including a cell having a first pore size, and (ii) a region in which the isotropic layer contacts a second portion of the interface layer, the region having a second pore size The first pore diameter is larger than the second pore diameter, the first portion of the interface layer includes a cell having the first pore diameter, and the second portion of the interface layer has the second pore diameter. A microfiltration membrane comprising a cell having is provided.

  [0024] In some embodiments, the asymmetric polymer layer has a first concentration and / or first viscosity polymer, and the isotropic polymer layer has a second concentration and / or second concentration. The interface layer includes a polymer in which the first concentration and the second concentration are mixed and / or the first viscosity and the second viscosity are mixed.

  [0025] Alternatively or in addition, in some embodiments, the interfacial film comprises a first polymer from the asymmetric layer and a second different polymer from the isotropic layer. including.

  [0026] In some embodiments of the membrane, the isotropic layer has a thickness of at least about 50 microns and / or the asymmetric layer has a thickness in the range of about 10 to about 15 microns.

  [0027] In one embodiment, the asymmetric layer is at least about 70% of the film thickness and / or the isotropic layer is at least about 30% of the film thickness.

  [0028] The asymmetric layer of the membrane can have an asymmetry of about 2 or more, or about 3 or more. In some embodiments, the asymmetry is in the range of about 10 to about 20.

  [0029] Another embodiment of the present invention provides: (a) a first asymmetric polymer layer having a first asymmetry ratio; and (b) a second asymmetric ratio greater than the first asymmetry ratio. Two asymmetric polymer layers; and (c) an interfacial polymer layer between the first asymmetric layer and the second asymmetric layer, the first portion contacting the first asymmetric layer and the second An interfacial polymer layer having a second portion in contact with the asymmetric layer, and (i) the first asymmetric layer has a region in contact with the first portion of the interface layer, and the region has a first pore diameter. (Ii) the second asymmetric layer has a region in contact with the second portion of the interface layer, the region includes a cell having a second pore size, and the first pore size is the second A precision larger than the pore size, wherein the first portion of the interface layer comprises a cell having a first pore size and the second portion of the interface layer comprises a cell having a second pore size To provide a filtration membrane.

  [0030] In some embodiments, the first asymmetric polymer layer and the second asymmetric polymer layer comprise different polymers, and the interface layer comprises a first polymer from the first asymmetric layer; And a second different polymer from the second asymmetric layer.

  [0031] In some embodiments, the first asymmetric polymer layer has an asymmetry rate in the range of about 0.5 to about 1.5, and / or the second asymmetric polymer layer is about It has an asymmetry ratio of 2 or more.

  [0032] In some embodiments, the membrane is a wrinkled membrane.

  [0033] In another embodiment, a method of using a membrane is provided. For example, a method of processing a fluid according to an embodiment of the present invention includes passing a fluid through a membrane in a direction from an asymmetric layer to an isotropic layer or in a direction from a second asymmetric layer to a first asymmetric layer. In a more preferred embodiment, the method comprises the step of passing a fluid through the membrane.

  [0034] In yet another embodiment, a precision having an asymmetric layer, an isotropic layer, and an interface layer having a first portion that contacts the asymmetric layer and a second portion that contacts the isotropic layer. The method of forming a filtration membrane includes: (a) preparing a first solution comprising a first polymer and a solvent for the first polymer; (b) a second polymer and the Preparing a second solution comprising a solvent for the second polymer, (c) casting the first solution onto the surface of the first support, and (d) about 2 seconds. Later, casting a second solution onto the first solution to form a pre-film, (e) exposing the pre-film to circulating air, and (f) the first solution in a non-solvent liquid And performing phase separation of the second solution.

  [0035] In another embodiment, a first asymmetric layer having a first asymmetry rate, a second asymmetric layer having a second asymmetry rate greater than the first asymmetry rate, and a first asymmetric layer A method for forming a microfiltration membrane according to an embodiment of the present invention having an interfacial polymer layer having a first portion in contact with the second asymmetric layer and a second portion in contact with the second asymmetric layer comprises: Preparing a first solution comprising a polymer of (1) and a solvent for the first polymer; (b) a second solution comprising a second polymer and a solvent for the second polymer. Preparing a second solution, (c) casting the first solution onto the surface of the first support, and (d) after a short time interval, placing the second solution on the first solution. Casting to form a pre-film, and (e) a first solution and a non-solvent solution. And a step of performing a phase separation of the second solution. The first and second polymers may be the same or different.

  [0036] The first and second polymers may be the same or different. In some method embodiments, the first solution has a first polymer of a first concentration and / or a first viscosity, and the second solution has a second concentration and / or a second Having a second polymer of viscosity.

  [0037] In a preferred method embodiment, casting the first solution comprises casting the first solution through a first preset gap provided by a first slot die or a first casting knife. And the step of casting the second solution comprises casting the second solution through a second preset gap provided by a second slot die or a second casting knife.

  [0038] In a more preferred method embodiment, at least one solution comprises polysulfone.

  [0039] Each of the components of the present invention will now be described in further detail. In this case, similar components have similar reference signs.

  [0040] The solution comprising the polymer is typically cast into a thin film one above the other, exposed to a gas environment for a predetermined period of time, and then quenched in a non-solvent for the polymer. Preferably, the first solution is diffused in a layer (lower layer) on a support (such as a non-porous support) and the second solution is layered on the first solution (upper layer). The membrane can then be separated from the support after quenching. However, if desired, a support (porous or non-porous) can be incorporated into the final structure.

  [0041] The film can be manually cast (eg, manually poured onto a casting surface, cast, or diffused to apply a quenching liquid onto this surface) or automatically cast (E.g. pouring onto a moving bed or otherwise casting). An example of a suitable support is polyethylene coated paper.

  [0042] There should be a time interval greater than 1 second, preferably greater than 1.5 seconds, between the casting of the first solution and the casting of the second solution onto the first solution. . The time interval is preferably about 2 seconds or more. For example, the time interval can be in the range of about 2 seconds to about 35 seconds, or about 2 seconds to about 10 seconds.

  [0043] Various devices known in the art can be used for casting. Suitable devices include, for example, a diffusion knife, a doctor blade, or a mechanical diffuser with an injection / pressurization system. An example of a diffusion device method is an extrusion die or slot coater with a casting chamber, which can introduce a casting compound (solution with polymer) into the casting chamber and extrude it through a narrow slot under pressure. . Illustratively, the first and second solutions comprising the polymer are applied by a doctor blade with a knife gap in the range of about 120 microns to about 500 microns, more typically in the range of about 180 microns to about 400 microns. Can be cast separately. The knife gap can be different for the first and second solutions.

  [0044] Various air gaps are suitable for use with the present invention, and the air gap can be the same or different for the knife and / or doctor blade. Typically, the air gap is in the range of about 3 inches to about 12 inches, more typically in the range of about 3.5 inches to about 6 inches.

  [0045] Various casting speeds are suitable, as is known in the art. Typically, the casting speed is at least about 2 feet per minute (fpm), for example when the knife air gap is at least about 3 inches.

  [0046] Illustratively, using a time interval of about 2 seconds between the casting of the first solution and the casting of the second solution, for a casting speed in the range of about 2.5 fpm to about 10 fpm, the air The gap can be in the range of about 4 inches to 16 inches. In another example, using a time interval of about 10 seconds between the casting of the first solution and the casting of the second solution, the air gap is about 4 for casting speeds in the range of about 10 fpm to about 20 fpm. It can be in the range of inches to 8 inches. Of course, the time interval can be longer than about 2 seconds, and the air gap and / or casting speed can be smaller or larger than the exemplary values listed above.

  [0047] The casting solution is preferably exposed to air after casting but before quenching. The air exposure time is usually in the range of about 2 seconds to about 35 seconds. Usually, the air is moist (eg, greater than about 60% relative humidity). In embodiments where the membrane comprises an asymmetric layer and an isotropic layer, air, eg, humid air, is circulated (eg, using one or more fans) to facilitate contact with the casting solution. Is preferred. In embodiments where the membrane comprises a first asymmetric layer and a second asymmetric layer, preferably no air is circulated.

  [0048] The support with the casting solution thereon is immersed in a cooling bath to effect phase separation of the polymer solution in a continuous layered arrangement to form an integral multilayer (ie under normal use conditions). In other words, a microporous polymer film is formed in which the layers are bonded together so that the films behave as a single structure that does not peel or separate. After formation, the membrane is usually washed (eg, in deionized water) to remove residual solvent, dried, and wound on a core.

  [0049] The quenching liquid is usually water, and the temperature of the quenching liquid is usually higher than the casting temperature. In the quench bath, precipitation or solidification occurs from the liquid film surface that first contacts the quench bath and then occurs through subsequent layers. Each layer dilutes and changes the quench fluid as the quench fluid diffuses through the layer.

  [0050] Suitable solutions containing polymers include polymers such as polycyclic aromatics, sulfones (eg, polyethersulfone (PES), bisphenol A polysulfone, polyarylsulfone, and aromatics such as polyphenylsulfone). Polysulfones including aromatic polysulfones), polyamides, polyimides, polyvinylidene halides (including polyvinylidene fluoride (PVDF)), polyolefins such as polypropylene and polymethylpentene, polyesters, polystyrenes, polycarbonates, polyacrylonitriles (including polyalkylacrylonitriles) , Cellulose polymers (such as cellulose acetate and cellulose nitrate), fluoropolymers, and PEEK. Examples of the solution including a polymer include a mixture of polymers, for example, a hydrophobic polymer (for example, a sulfone polymer) and a hydrophilic polymer (for example, polyvinylpyrrolidone).

  [0051] Typically, a solution comprising a polymer has an absorbance of about 0.05 or greater at 310 nm at room temperature, for example, the absorbance can range from about 0.01 to about 0.3 at 310 nm. In some embodiments, the first casting solution (forming the lower layer) has a higher absorbance than the subsequent casting solution (forming the upper layer).

  [0052] In addition to one or more polymers, a typical solution may comprise at least one solvent and further comprise at least one non-solvent. Suitable solvents include, for example, dimethylformamide (DMF); N, N-dimethylacetamide (DMAC); N-methylpyrrolidone (NMP); tetramethylurea; dioxane; diethyl succinate; dimethyl sulfoxide; chloroform; Mention may be made of chloroethane, as well as mixtures thereof. Suitable non-solvents include, for example, water; various polyethylene glycols (PEG; eg PEG-400, PEG-1000); various alcohols such as methanol, ethanol, isopropyl alcohol (IPA), amyl alcohol, hexanol, heptanol Alkanes such as hexane, propane, nitropropane, heptane and octane; ketones, ethers and esters such as acetone, butyl ether, ethyl acetate and amyl acetate; and various salts, For example, calcium chloride, magnesium chloride, lithium chloride, and mixtures thereof.

  [0053] If desired, the solution comprising the polymer may be, for example, one or more polymerization initiators (eg, peroxide, ammonium persulfate, aliphatic azo compounds (eg, 2,2′-azobis (2-amidino Propane) dihydrochloride (V50)), and any one or more of these combinations), and / or trace content, such as surfactants and / or strippers. .

  [0054] Suitable solution components are known in the art. Exemplary solutions comprising polymers, and exemplary solvents and non-solvents are described, for example, in US Pat. Nos. 5,846,422, 5,906,742, 5,928,774. No. 6,045,899, and 6,146,747.

  [0055] According to the present invention, the layers of the membrane can be formed from the same polymer and solvent, various viscosities, additives, and treatments, or different polymers can be used in different layers. it can.

  [0056] An isotropic layer has a porous structure with a distribution characterized by approximately the same average pore structure across the layer. For example, with respect to pore size, an isotropic layer has a pore size distribution characterized by approximately the same pore size across the layer.

  [0057] An asymmetric layer has a pore structure (usually pore size) that varies throughout the layer. Typically, the pore size decreases in diameter from one part or surface to another part or surface (eg, the pore size of the cell decreases from an upstream part or surface to a downstream part or surface). However, other types of asymmetry are encompassed by embodiments of the present invention. For example, the pore diameter forms a minimum pore diameter at a position within the thickness range of the asymmetric layer. The asymmetric layer can have any suitable pore size gradient or pore size ratio, such as about 0.5 or more, about 3 or more, or about 7 or more, or in the range of about 0.5 to about 1.5, about 2: 1. To about 20: 1, or about 3: 1 to about 10: 1. This asymmetry can be measured by comparing the hole diameter on one main surface of one layer with the hole diameter of the other main surface of the layer.

  [0058] Typically, the isotropic layer has a pore structure (usually a pore size) in the range of about 0.02 microns to about 0.3 microns.

  [0059] The thickness of each layer can be varied within a wide range while still obtaining a self-supporting monolithic multilayer. Typically, the multilayer film has a thickness of at least about 50 microns, more typically at least about 75 microns, preferably at least about 100 microns. Typically, in embodiments including an isotropic layer, the isotropic layer and the interfacial polymer layer are each in the range of about 15% to about 33% of the total thickness, and the asymmetric layer is the total thickness. Of about 60% to about 70%. Typically, in embodiments including the first and second asymmetric layers, the first asymmetric layer and the interface layer together are about 8% to about 15% of the total thickness, and the second The asymmetric layer is about 75% to about 90% of the total film thickness.

  [0060] According to an embodiment of the invention, a filter and a filter element are also provided, in which case the filter and the filter element comprise at least one membrane according to the invention.

[0061] Membranes according to the present invention (and filter elements comprising at least one membrane) may be of any suitable pore structure, eg pore size (eg porometry (eg mercury porometry or capillary condensate flow porometry)). or by bubble point, or, as evidenced by _{K L} as described, for example, U.S. Pat. No. 4,340,479), the hole ratio, pore size (e.g., U.S. Patent No. 4,925, (E.g., using a modified OSU F2 test as described in 572 or as characterized using a porometer), or as one or more membranes of the material of interest as fluid is passed through the element It can have a removal ratio that reduces or allows passage. The desired pore structure depends on the composition of the fluid to be treated and the desired outflow level of the treated fluid.

[0062] The membrane can have any desired critical wet surface tension (CWST, eg, as defined in US Pat. No. 4,925,572). CWST can be selected as known in the art, for example, US Pat. Nos. 5,152,905, 5,443,743, 5,472,621, And can be selected as further disclosed in US Pat. No. 6,074,869. For applications where the liquid passes through the membrane, the membrane has a CWST of 72 dynes / cm (about 72 × 10 ⁻⁵ N / cm) or more, more preferably about 78 dynes / cm (about 78 × 10 ⁻⁵ N). / Cm) or more hydrophilic (with the completed state or post-treatment). However, for some other applications where liquid does not pass through the membrane (eg, for venting applications), the membrane is hydrophobic with a CWST of less than 72 dynes / cm (about 72 × 10 ⁻⁵ N / cm). Can be.

  [0063] The surface properties of the film can be determined by wet or dry oxidation, by coating or depositing a polymer on the surface, or by a grafting reaction (eg, affecting CWST, eg, surface charge, eg, It can be modified to include a positive or negative charge and / or to change the polarity or hydrophilicity of the surface. Modifications include, for example, irradiation with polar or charged monomers, coating and / or curing surfaces with charged polymers, and chemical attachment to attach functional groups on the surface. Modification may be mentioned. The grafting reaction can be by exposure to energy sources such as gas plasma, vapor plasma, corona discharge, heat, van der graph generator, ultraviolet light, electron beam, or by various other forms of radiation. Alternatively, it may be activated by surface etching or deposition using plasma treatment.

  [0064] Membranes according to embodiments of the present invention may be used, for example, for bacterial filtration applications, fluid filtration in the electronics industry, fluid filtration in the pharmaceutical industry, fluid filtration in the food and beverage industry, purification, antibody- and / or protein-containing fluids. It can be used in various applications including filtration, filtration of cell culture fluids, and aeration.

  [0065] A filter and / or filter element comprising at least one membrane according to the invention has at least one of different structures and / or functions, for example pre-filters, support materials, drainage, spacers and cushioning materials. Additional elements, layers, or components that can have Illustratively, the filter may also include at least one additional element such as a mesh and / or a screen.

  [0066] According to embodiments of the present invention, the membrane, filter, and / or filter element can have a variety of forms, including planar, barbed, and hollow cylindrical.

  [0067] In some embodiments, a filter comprising a plurality of filter elements is typically disposed within a housing, the housing comprising at least one inlet and at least one outlet, and between the inlet and outlet. At least one fluid flow path is formed, and the filter traverses the fluid flow path to provide a filter device. The filter device is preferably sterilizable. Any housing having a suitable shape and comprising at least one inlet and at least one outlet may be used.

  [0068] The following examples further illustrate the present invention, but of course should not be construed to limit the scope of the invention in any way.

  [0069] In the following examples, the membrane is manufactured using a system generally positioned as shown in FIG. A casting solution is described in each example. The membrane is cast on paper using a casting knife. Knife 1 and knife 2 are used with a preset air gap and under the conditions listed below. Six fans are used to provide air velocity. After casting, the membrane is quenched in the water bath for 6 minutes until it solidifies (the water bath quench temperature is 105 ° F. (about 41 ° C.)). The membrane is further washed overnight with deionized water and then oven dried.

  [0070] The pore size is analyzed using a Quantachrome PoreMaster® (series mercury intrusion porosimeter (Boynton Beach, Florida) and Porvair porometer (Porvair plc, Norfolk, UK).

[0071] The casting conditions of Examples 1-5 are as follows.

  [0072] This example is a film having an isotropic polymer layer, an asymmetric polymer layer, and an interface layer, the asymmetric layer having a region in contact with the first portion of the interface layer; The region includes a cell having a first pore size, the isotropic layer includes a region in contact with another portion of the interface layer, the region includes a cell having a second pore size, and the first pore size is the second A membrane according to an embodiment of the invention, wherein the first portion of the interface layer comprises a cell having a first pore size and the second portion of the interface layer comprises a cell having a second pore size. Will be described.

  [0073] Solution 1 (top) consists of 11.5% PES, 5% water, 0.5% sulfonated PES (SPES), 3% PVP (polyvinylpyrrolidone) (k-90), 25% It consists of PEG200 and 55% NMP. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

  [0074] A SEM cross-sectional view of the membrane is shown in FIG.

  [0075] The isotropic layer is 19 microns (μm) thick and the pore size is 0.15 μm. The interface layer is 7 μm thick, in which case the region of the interface layer in contact with the isotropic layer has 0.15 μm pore cells and the region of the interface layer in contact with the asymmetric layer has 1 μm pore cells. The area of the interface layer between the two areas has a pore size of 0.5 μm. The asymmetric layer is 111 μm thick, in which case the region of the asymmetric layer in contact with the interface layer has a pore size of 1 μm and the other surface of the asymmetric layer has a pore size of 10 μm (asymmetry rate = 10).

  [0076] This example is a film having an isotropic polymer layer, an asymmetric polymer layer, and an interface layer, the asymmetric layer having a region in contact with the first portion of the interface layer; The region includes a cell having a first pore size, the isotropic layer includes a region in contact with another portion of the interface layer, the region includes a cell having a second pore size, and the first pore size is Another embodiment of the present invention wherein the first portion of the interface layer comprises a cell having a first pore size and the second portion of the interface layer comprises a cell having a second pore size, wherein the first portion of the interface layer comprises a cell having a second pore size. The formation of the film according to the above will be described.

  [0077] Solution 1 (top) consists of 11.5% PES, 5% water, 0.5% sulfonated PES (SPES), 3% PVP (k-90), 25% PEG200, 55 % NMP. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

  [0078] A SEM cross-sectional view of the membrane is shown in FIG.

  [0079] The isotropic layer is 12 μm thick and the pore diameter is 0.15 μm. The interface layer is 39 μm thick, in which case the region of the interface layer that contacts the isotropic layer has 0.15 μm pore size cells and the region of the interface layer that contacts the asymmetric layer has 0.6 μm pore size cells. The area of the interface layer between the two areas has a pore size of 0.5 μm. The asymmetric layer is 81 μm thick, in which case the region of the asymmetric layer in contact with the interface layer has a pore size of 0.6 μm and the other surface of the asymmetric layer has a pore size of 3 μm (asymmetric ratio = 5) .

  [0080] This example is a film according to another embodiment of the invention having an isotropic polymer layer, an asymmetric polymer layer, and an interface layer, wherein the asymmetric layer is the first of the interface layers. A region in contact with the portion, the region including a cell having a first pore size, the isotropic layer having a region in contact with another portion of the interface layer, and the region having a second pore size. A cell including a cell, the first pore diameter being larger than the second pore diameter, the first portion of the interface layer having a first pore diameter, and the second portion of the interface layer having a second pore diameter The formation of a film according to another embodiment of the present invention, comprising:

  [0081] Solution 1 (top) consists of 11.5% PES, 5% water, 0.5% sulfonated PES (SPES), 3% PVP (k-90), 25% PEG200, 55 % NMP. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

  [0082] A SEM cross-sectional view of the membrane is shown in FIG.

  [0083] The isotropic layer is 7 μm thick and the pore diameter is 0.5 μm. The interface layer is 12 μm thick, in which case the region of the interface layer in contact with the isotropic layer has 0.5 μm pore cells and the region of the interface layer in contact with the asymmetric layer has 1 μm pore cells. The area of the interface layer between the two areas has a pore size of 0.15 μm. The asymmetric layer is 104 μm thick, where the region of the asymmetric layer in contact with the interface layer has a pore size of 1 μm and the other surface of the asymmetric layer has a pore size of 10 μm (asymmetry rate = 10).

  [0084] This example illustrates forming a film according to another embodiment of the present invention.

  [0085] Solution 1 (top) is 10.8% PES, 5% water, 3% glycerin, 25% PEG200, 0.05% V-50 (2,2 provided by Wako Chemical, Richmond, VA) '-Azobis (2-amidinopropane) dihydrochloride azo initiator), 0.1% HEMA (hydroxyl ethyl methacrylate), 0.3% PEGDMA (polyethylene glycol dimethacrylate), 0.2% PTA (Milwaukee, Wis.) The pentaerythritol tetraacrylate provided by Aldrich chemical Co.), NMP balance to 100%. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

  [0086] A SEM cross-sectional view of the membrane is shown in FIG.

  [0087] The isotropic layer is 10 μm thick and the pore diameter is 0.3 μm. The interface layer is 43 μm thick, in which case the interface layer region in contact with the first isotropic layer has a 0.3 μm pore size cell and the interface layer region in contact with the asymmetric layer is a 0.5 μm pore size cell. And the region of the interface layer between the two regions has a pore size of 0.5 μm. The asymmetric layer is 65 μm thick, in which case the region of the asymmetric layer in contact with the interface layer has a pore size of 0.5 μm and the other surface of the asymmetric layer has a pore size of 2 μm (asymmetry rate = 4).

  [0088] This example illustrates forming a film according to another embodiment of the present invention.

  [0089] Solution 1 (top) is 10.8% PES, 5% water, 3% glycerin, 25% PEG200, 0.05% V-50 (an azo initiator provided by Wako Chemical), 0.1% HEMA, 0.3% PEGDMA, 0.2% PTA (pentaerythritol tetraacrylate provided by Aldrich chemical Company), NMP balance to match 100%. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

  [0090] A SEM cross-sectional view of the membrane is shown in FIG.

  [0091] The isotropic layer is 35 μm thick and the pore diameter is 0.1 μm. The interface layer is 35 μm thick, in which case the interface layer region in contact with the first isotropic layer has a 0.1 μm pore cell and the interface layer region in contact with the asymmetric layer is a 0.5 μm pore cell. And the region of the interface layer between the two regions has a pore size of 0.25 μm. The asymmetric layer is 65 μm thick, in which case the region of the asymmetric layer in contact with the interface layer has a pore size of 0.5 μm and another surface of the asymmetric layer has a pore size of 2 μm (asymmetric factor = 4).

  [0092] This example is a film having first and second asymmetric polymer layers and an interface layer, wherein the first asymmetric layer has a region in contact with the first portion of the interface layer. Wherein the region includes a cell having a first pore size, the second asymmetric layer has a region in contact with another portion of the interface layer, the region includes a cell having a second pore size, and the first Implementation of the invention wherein the pore size is larger than the second pore size, the first portion of the interface layer comprises a cell having a first pore size, and the second portion of the interface layer comprises a cell having a second pore size Generation of the film according to the embodiment will be described.

  [0093] The system used to produce this membrane differs from the system shown in FIG. 1 in that no fan is used, ie, no air is circulated.

  [0094] The following solutions are used.

  [0095] Solution 1 (top) is 10.7% polysulfone, 16.1% t-amyl alcohol, 73.2% DMF. Solution 2 (bottom) consists of 11% PES, 5% water, 5% PVP (k-90), 25% PEG200, and 54% NMP.

[0096] The casting conditions for Example 6 are as follows.

  [0097] A SEM cross-sectional view of the membrane is shown in FIG.

  [0098] The first asymmetric layer is 7 μm thick, the portion of the first asymmetric layer in contact with the interface layer has cells with a pore size of 0.02 μm, and the pore size of the other surface is 0.5 μm Yes (asymmetry rate = 25).

  [0099] The interface layer is 10 μm thick, where the region of the interface layer in contact with the first asymmetric layer has 0.02 μm pore size cells and the region of the interface layer in contact with the second asymmetric layer is 0 .05 μm pore size cell, the region of the interface layer between the two regions has a pore size of 0.1 μm. The second asymmetric layer is 85 μm thick, where the region of the asymmetric layer in contact with the interface layer has a pore size of 0.1 μm, and the other surface of the asymmetric layer has a pore size of 0.5 μm (asymmetric ratio = 5).

  [00100] This example demonstrates the good water flow and throughput provided by membranes according to embodiments of the present invention.

  [00101] The membrane is manufactured as described in Example 3. In addition, commercially available isotropic membranes and asymmetric membranes can be obtained. The isotropic membrane is a SUPOR® 200 polyethersulfone membrane having a pore size of 0.2 μm, and the asymmetric membrane has a pore size of 0.2 μm on the skin surface and a pore size of 20 μm on the other surface. (Asymmetric factor = 10) BTS-55 polysulfone membrane, both membranes available from Pall Corporation (East Hills, NY).

  [00102] A 1% molasses solution is produced (5 grams molasses (Lesle molasses, Notts, UK); dissolved in 495 grams deionized water (DI)). The membrane is placed in the test cell, the test system is purged, and the throughput is determined for 10 minutes at 3 psi.

[00103] In addition, DI water flow rate in the 10 psi (ml / min) is determined in 90mm disk, Similarly, _{K L} bubble point (psi) and MFP (mean flow pore) size ([mu] m) is also determined.

  [00104] The results are as follows.

[00105] film of the present invention, 1% molasses throughput 220 for 10 minutes at 3 psi, DI water flow rate of 2800 ml / min at 10 psi, _{K L} bubble point of 50 psi, and, with a MFP size of 0.27 [mu] m.

[00106] Isotropic membranes have 1% molasses throughput 10 for 10 minutes at 3 psi, DI water flow rate of 1200 ml / min at 10 psi, _{K L} bubble point of 55 psi, and the 0.25μm of MFP size.

[00107] Asymmetric membranes, 1% molasses throughput 45 for 10 minutes at 3 psi, DI water flow rate of 1600 ml / min at 10 psi, _{K L} bubble point of 55 psi, and, with a MFP size of 0.24 .mu.m.

  [00108] All documents, including publications, patent applications, patents cited herein, are individually and specifically indicated by reference as if each document was incorporated by reference. Are incorporated herein to the same extent as if set forth in full herein.

  [00109] The use of the terms "a" and "an" and "the" and similar referents in the context of the description of the invention is described elsewhere herein. Unless otherwise indicated, or unless clearly contradicted by context, this should be interpreted to cover both singular and plural. The terms “comprising”, “having”, “including”, and “including”, unless stated otherwise, mean unrestricted terms (ie, “including but not limited to”). Should be interpreted as The recitation of value ranges herein is intended to serve as a convenient way to individually indicate each distinct value that falls within that range, unless otherwise indicated herein. Also, each distinct value is incorporated into the specification as if it were individually listed herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any example, all examples, or exemplary wording (eg, “etc.”) provided herein is merely intended to better illustrate the invention and is defined by the following claims. Unless otherwise stated, the scope of the present invention is not limited. No language in the specification should be construed as considering any element not recited in the claims as essential to the practice of the invention.

  [00110] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations on these preferred embodiments will be apparent to those skilled in the art upon understanding the foregoing description. The inventors contemplate that those skilled in the art will use such variations as necessary, and that the inventors have developed the invention in ways other than those specifically described herein. Is intended to be implemented. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims (13)

(A) an asymmetric polymer layer;
(B) an isotropic polymer layer;
(C) an interfacial polymer layer between the asymmetric layer and the isotropic layer, comprising a first portion that contacts the asymmetric layer and a second portion that contacts the isotropic layer; An interfacial polymer layer,
(I) the asymmetric layer has a region in contact with the first portion of the interface layer, the region including a cell having a first pore diameter;
(Ii) The isotropic layer has a region in contact with the second portion of the interface layer, the region includes a cell having a second pore size, and the first pore size is the second pore size. Bigger than
A microfiltration membrane wherein the first portion of the interface layer includes a cell having the first pore diameter, and the second portion of the interface layer includes a cell having the second pore diameter.   The membrane of claim 1, wherein the asymmetric layer has an asymmetry of about 2 or greater. (A) a first asymmetric polymer layer having a first asymmetry rate;
(B) a second asymmetric polymer layer having a second asymmetry rate greater than the first asymmetry rate;
(C) an interfacial polymer layer between the first asymmetric layer and the second asymmetric layer, the first portion contacting the first asymmetric layer, and the second asymmetric layer; An interfacial polymer layer having a second portion in contact with,
(I) the first asymmetric layer includes a region in contact with the first portion of the interface layer, the region including a cell having a first pore diameter;
(Ii) the second asymmetric layer includes a region in contact with the second portion of the interface layer, the region including a cell having a second pore diameter;
The first hole diameter is larger than the second hole diameter, the first portion of the interface layer includes a cell having the first hole diameter, and the second portion of the interface layer is the second hole. A microfiltration membrane comprising a cell having a pore size.   The microfiltration membrane of claim 3, wherein the first asymmetric polymer layer has an asymmetry ratio in the range of about 0.5 to about 1.5.   The microfiltration membrane according to claim 3 or 4, wherein the second asymmetric polymer layer has an asymmetry ratio of about 2 or more.   The microfiltration membrane according to any one of claims 1 to 5, comprising a ridged membrane.   A method of treating a fluid comprising passing the fluid in a direction from the asymmetric layer toward the isotropic layer through a membrane according to any one of claims 1, 2, or 6.   A method of treating a fluid comprising passing the fluid through a membrane according to any one of claims 3-6 in a direction from the second asymmetric layer toward the first asymmetric layer. How to prepare.   9. A method according to claim 7 or 8, comprising the step of passing the fluid through the membrane. A method of forming a microfiltration membrane having an asymmetric layer, an isotropic layer, and an interface layer having a first portion in contact with the asymmetric layer and a second portion in contact with the isotropic layer. ,
(A) preparing a first solution comprising a first polymer and a solvent for the first polymer;
(B) preparing a second solution comprising a second polymer and a solvent for the second polymer;
(C) casting the first solution onto the surface of the first support;
(D) after about 2 seconds, casting the second solution onto the first solution to form a pre-film;
(E) exposing the pre-membrane to circulating air;
(F) performing phase separation of the first solution and the second solution in a non-solvent liquid. A first asymmetric layer having a first asymmetry ratio; a second asymmetric layer having a second asymmetry ratio greater than the first asymmetric ratio; and a first portion in contact with the first asymmetric layer. And forming a microfiltration membrane having an interface layer having a second portion in contact with the second asymmetric layer,
(A) preparing a first solution comprising a first polymer and a solvent for the first polymer;
(B) preparing a second solution comprising a second polymer and a solvent for the second polymer;
(C) casting the first solution onto the surface of the first support;
(D) after about 2 seconds, casting the second solution onto the first solution to form a pre-film;
(E) performing phase separation of the first solution and the second solution in a non-solvent liquid.   The method according to claim 10 or 11, wherein at least one of the solutions comprises polysulfone.   Casting the first solution comprises casting the first solution through a first preset gap provided by a first slot die or a first casting knife, the second solution The method of any of claims 10-12, wherein casting the solution comprises casting the second solution through a second preset gap provided by a second slot die or a second casting knife. The method according to one item.